文章
Dummer. ゛☀
2017年09月19日
Anthracnose is a group of related fungal leaf and stem diseases that infect shade trees. Maple anthracnose is not the same disease as oak anthracnose, although the symptoms of these diseases may be quite similar. Anthracnose diseases generally infect the leaf veins and cause death of the vein and surrounding tissue. Control of anthracnose diseases follows the same procedure for all shade trees affected. The disease does not cause the death of the host but may reduce growth over successive seasons of complete defoliation.
Symptoms and Diagnosis
Irregular, light brown spots of dead tissue develop along the veins of the leaves. Affected plants may have the appearance of being sun-scorched. Sunken cankers containing fungal spores develop on infected twigs of some trees, such as sycamore.
Life Cycle
Anthracnose fungi overwinter on fallen leaves and twigs that were infected the proceeding year. Infection is favored by cool, moist weather in the spring of the year. Infection can occur on the vulnerable young leaves when there is a film of water on the leaf surface. Infection is typically more severe on the lower third of the tree, where the humidity is the highest.
Integrated Pest Management Strategies
1. Collect and destroy infected leaves as they fall. Infected leaves and twigs that remain in the vicinity are a source of spores for new infections in the spring.
2. Prune out dead branches. Be sure to clean all garden tools to avoid the spread of the disease. A 1–part bleach to 9–part water solution can be used to dip tools into between cuts.
3. Promote air circulation. Thin out excessive twig and branch growth. This will reduce the period of time that leaves are wet and vulnerable to inoculation.
4. Keep trees growing vigorously. Supply 1–2 inches of water weekly only during dry periods. Fertilize early in the spring or in late fall.
5. Spray with a fungicide when leaves are beginning to enlarge from the buds. Reapply at 7–10 day intervals for two or three more times. Fungicide sprays are most appropriate for younger, newly transplanted trees that may not be able to withstand defoliation. The available fungicides are preventive, not curative, and therefore, must be applied before spotting occurs. Commonly used products include copper, chlorothalonil (Daconil), captan, ferbam, mancozeb, maneb, and thiram. Your pesticide choice should be based on the particular problem you are seeking to control. Consult an arborist for difficult situations and where power equipment is required.
Symptoms and Diagnosis
Irregular, light brown spots of dead tissue develop along the veins of the leaves. Affected plants may have the appearance of being sun-scorched. Sunken cankers containing fungal spores develop on infected twigs of some trees, such as sycamore.
Life Cycle
Anthracnose fungi overwinter on fallen leaves and twigs that were infected the proceeding year. Infection is favored by cool, moist weather in the spring of the year. Infection can occur on the vulnerable young leaves when there is a film of water on the leaf surface. Infection is typically more severe on the lower third of the tree, where the humidity is the highest.
Integrated Pest Management Strategies
1. Collect and destroy infected leaves as they fall. Infected leaves and twigs that remain in the vicinity are a source of spores for new infections in the spring.
2. Prune out dead branches. Be sure to clean all garden tools to avoid the spread of the disease. A 1–part bleach to 9–part water solution can be used to dip tools into between cuts.
3. Promote air circulation. Thin out excessive twig and branch growth. This will reduce the period of time that leaves are wet and vulnerable to inoculation.
4. Keep trees growing vigorously. Supply 1–2 inches of water weekly only during dry periods. Fertilize early in the spring or in late fall.
5. Spray with a fungicide when leaves are beginning to enlarge from the buds. Reapply at 7–10 day intervals for two or three more times. Fungicide sprays are most appropriate for younger, newly transplanted trees that may not be able to withstand defoliation. The available fungicides are preventive, not curative, and therefore, must be applied before spotting occurs. Commonly used products include copper, chlorothalonil (Daconil), captan, ferbam, mancozeb, maneb, and thiram. Your pesticide choice should be based on the particular problem you are seeking to control. Consult an arborist for difficult situations and where power equipment is required.
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文章
Dummer. ゛☀
2017年09月19日
Algal leaf spot is a foliar disease most commonly seen in warm humid climates or in greenhouses. The causal organism is Cephaleuros virescens, a green parasitic alga whose usual hosts are plants with leathery leaves such as cotoneasters, magnolias, hollies, rhododendrons and viburnums. Algal leaf spot is sometimes called green scurf because the spots may have a crusty, fuzzy or flaky appearance.
Symptoms and Diagnosis
Algal leaf spot is characterized by grayish, green, brown or orange cushion-like blotches on the leaf surface. Some hosts may also have diseased twigs and branches that are girdled and stunted with reddish brown fruiting bodies. The spots are generally 1/2 inch or less in diameter although they may coalesce to form larger colonies. Leaf tissue may die beneath the spots and the leaves may yellow and drop prematurely.
Life Cycle
During wet weather, the algae produce spores that are spread by wind and splashing rain. The spores infect leaf tissue causing small, greenish circular spots that may age to light brown or reddish brown. The spots may appear raised and velvety. The algae will overwinter or survive other unfavorable environmental conditions in leaf spots including those on fallen leaves.
Integrated Pest Management Strategies
1. Encourage healthy plants with good cultural techniques. This disease is most damaging on plants that are already slow-growing or weakened.
2. Clean up fallen leaves and remove diseased leaves from the plant. Good sanitation practices will help control this disease.
3. Promote dry leaves by improving air circulation and drainage. If necessary, selectively prune overcrowded vegetation. Avoid spraying water on the leaves.
4. Use fungicidal sprays containing copper if chemical control is necessary
Symptoms and Diagnosis
Algal leaf spot is characterized by grayish, green, brown or orange cushion-like blotches on the leaf surface. Some hosts may also have diseased twigs and branches that are girdled and stunted with reddish brown fruiting bodies. The spots are generally 1/2 inch or less in diameter although they may coalesce to form larger colonies. Leaf tissue may die beneath the spots and the leaves may yellow and drop prematurely.
Life Cycle
During wet weather, the algae produce spores that are spread by wind and splashing rain. The spores infect leaf tissue causing small, greenish circular spots that may age to light brown or reddish brown. The spots may appear raised and velvety. The algae will overwinter or survive other unfavorable environmental conditions in leaf spots including those on fallen leaves.
Integrated Pest Management Strategies
1. Encourage healthy plants with good cultural techniques. This disease is most damaging on plants that are already slow-growing or weakened.
2. Clean up fallen leaves and remove diseased leaves from the plant. Good sanitation practices will help control this disease.
3. Promote dry leaves by improving air circulation and drainage. If necessary, selectively prune overcrowded vegetation. Avoid spraying water on the leaves.
4. Use fungicidal sprays containing copper if chemical control is necessary
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文章
Dummer. ゛☀
2017年09月18日
Rhizosphaera needlecast is caused by the fungus, Rhizosphaera kalkhoffii. The disease causes death and casting (dropping) of needles in spruces, especially Colorado spruce and occasionally white spruce. It is usually first evident on the lower branches of the tree and can cause severe defoliation and death of branches if allowed to persist. It rarely kills the tree.
Symptoms and Diagnosis
Infections take place in the spring, and symptoms show up about a year later. Infected 2-year old needles become spotted or mottled, some turning yellow and some developing a purplish brown color in late summer. Browning becomes general in late winter to early spring, and needles are prematurely shed during summer and fall, 12 to 15 months after initial infection. Black fruiting bodies are visible on discolored needles and even some green ones. The spores emerge from the stomates on the needles so appear in rows along the needles. Scattered lower branches are usually affected first and then browning progresses upward. Symptoms may be confused with spider mite damage. In the latter, mites and fine webbing may be visible; the lines of black fruiting bodies on the needles will also be absent.
Life Cycle
Rhizosphaera kalkhoffii overwinters in infected needles on the tree or ground. Spores are released from the infected needles in the spring, during wet weather. Spores are dispersed by splashing and dripping water. They infect newly emerging needles, as well as mature needles. Infection begins in spring, in April or May. Optimal temperature for fungal development on wet foliage is 77° F. Infection will occur in 48 hours if spores are present. Prolonged wetness can induce extensive infection.
Integrated Pest Management Strategies
1. Select healthy plants. If spruce trees are dropping their needles, avoid using these trees in the landscape.
2. Remove infected needles and branches during dry, sunny weather. Prune out diseased branches and rake up fallen needles. Burn or remove the collected debris. Disinfect pruning tools between cuts by dipping in a 10% chlorine bleach solution. Oil tools when done to inhibit rust.
3. Avoid overhead watering.Water on the foliage can promote infection. Spores require moisture to germinate and infect.
4. Improve air circulation to allow needles to dry more quickly. Maintain open spacing when planting or by mowing grass or brush.
5. Use fungicidal sprays. Severe infections should be sprayed with chlorothalonil (Daconil), thiophanate methyl (Cleary 3336), or copper-containing fungicides registered for use against this disease. Spray when the needles are half-elongated and again when fully elongated. A minimum of two years of treatment is recommended because of the organism's life cycle.
Symptoms and Diagnosis
Infections take place in the spring, and symptoms show up about a year later. Infected 2-year old needles become spotted or mottled, some turning yellow and some developing a purplish brown color in late summer. Browning becomes general in late winter to early spring, and needles are prematurely shed during summer and fall, 12 to 15 months after initial infection. Black fruiting bodies are visible on discolored needles and even some green ones. The spores emerge from the stomates on the needles so appear in rows along the needles. Scattered lower branches are usually affected first and then browning progresses upward. Symptoms may be confused with spider mite damage. In the latter, mites and fine webbing may be visible; the lines of black fruiting bodies on the needles will also be absent.
Life Cycle
Rhizosphaera kalkhoffii overwinters in infected needles on the tree or ground. Spores are released from the infected needles in the spring, during wet weather. Spores are dispersed by splashing and dripping water. They infect newly emerging needles, as well as mature needles. Infection begins in spring, in April or May. Optimal temperature for fungal development on wet foliage is 77° F. Infection will occur in 48 hours if spores are present. Prolonged wetness can induce extensive infection.
Integrated Pest Management Strategies
1. Select healthy plants. If spruce trees are dropping their needles, avoid using these trees in the landscape.
2. Remove infected needles and branches during dry, sunny weather. Prune out diseased branches and rake up fallen needles. Burn or remove the collected debris. Disinfect pruning tools between cuts by dipping in a 10% chlorine bleach solution. Oil tools when done to inhibit rust.
3. Avoid overhead watering.Water on the foliage can promote infection. Spores require moisture to germinate and infect.
4. Improve air circulation to allow needles to dry more quickly. Maintain open spacing when planting or by mowing grass or brush.
5. Use fungicidal sprays. Severe infections should be sprayed with chlorothalonil (Daconil), thiophanate methyl (Cleary 3336), or copper-containing fungicides registered for use against this disease. Spray when the needles are half-elongated and again when fully elongated. A minimum of two years of treatment is recommended because of the organism's life cycle.
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文章
Dummer. ゛☀
2017年09月18日
Procera root rot also known as white pine root decline is caused by the fungus Leptographium procerum (syn. Verticicladiella procera). It infects the inner bark and sapwood of the roots and lower trunk of white pine. Although the disease is most serious on white pine, it can also kill Scots and Austrian pines.
Symptoms and Diagnosis
In the Spring, trees, aged 3 to 15 years, which have been infected for several years, show delayed bud break and reduced candle elongation. Mature foliage then fades, droops, and turns brown, in stark contrast to healthy trees nearby. Mortality appears to be at random with a few trees dying each year. Resin flow is visible at the tree base and is associated with a girdling chocolate brown to dark olive-brown canker under the bark. The trunk may be flattened on the affected side. Galleries of insects such as the pine root collar weevil may be found in the canker and provide a place for the fungus to sporulate. Weevils and other bark-infesting insects may serve as vectors for this disease. Although the fungus does not survive well in the soil, it may be spread by contaminated insects as they emerge from diseased trees and feed on healthy trees nearby.
Integrated Pest Management Strategies
1. Planting. Avoid planting eastern white pine on wet sites. Trees planted on wet sites seem to be more susceptible to the fungus. Excessively dry sites also seem to predispose trees to attack.
2. Sanitation. Remove and destroy infected trees including stumps, if possible. Do not replant eastern white pine among the stumps of recently killed trees.
3. Replant. If trees need to be replaced, do not plant a pine. Use arborvitae or spruce.
Symptoms and Diagnosis
In the Spring, trees, aged 3 to 15 years, which have been infected for several years, show delayed bud break and reduced candle elongation. Mature foliage then fades, droops, and turns brown, in stark contrast to healthy trees nearby. Mortality appears to be at random with a few trees dying each year. Resin flow is visible at the tree base and is associated with a girdling chocolate brown to dark olive-brown canker under the bark. The trunk may be flattened on the affected side. Galleries of insects such as the pine root collar weevil may be found in the canker and provide a place for the fungus to sporulate. Weevils and other bark-infesting insects may serve as vectors for this disease. Although the fungus does not survive well in the soil, it may be spread by contaminated insects as they emerge from diseased trees and feed on healthy trees nearby.
Integrated Pest Management Strategies
1. Planting. Avoid planting eastern white pine on wet sites. Trees planted on wet sites seem to be more susceptible to the fungus. Excessively dry sites also seem to predispose trees to attack.
2. Sanitation. Remove and destroy infected trees including stumps, if possible. Do not replant eastern white pine among the stumps of recently killed trees.
3. Replant. If trees need to be replaced, do not plant a pine. Use arborvitae or spruce.
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文章
Dummer. ゛☀
2017年09月18日
Phomopsis blight is a serious disease problem on eastern red cedar in Missouri. The fungal disease, caused by Phomopsis juniperovora, is widespread in this region and can infect arborvitae and cypress as well as juniper. Phomopsis is more of a problem on junipers in landscape plantings because young tissue is most seriously infected. Older plants are seldom killed by Phomopsis, thus it is not a concern in natural stands of juniper.
Symptoms and Diagnosis
The first sign of infection is the browning of needle tips. New shoots, in the yellow-green stage, will brown and die in their first summer. Progressive dieback follows, eventually killing an entire branch by girdling the stem. The fungus will progress to the main stem and can infect and girdle stems less than 1/2 inch in diameter. Infected needles turn light green, then reddish-brown, and finally an ashen gray.
Life Cycle
Phomopsis overwinters on needles and stems of young trees that were infected the previous year. The fungus is most abundant on dead tissue that has become ashen gray in color. Infective spores are dispersed by rain splash. Only seven hours of 100% humidity are needed for infection to occur when temperatures are 75 degrees F.
Integrated Pest Management Strategies
1. Prune infected branches to prevent the spread of the disease. Remove dead tissue as well. The fungus can produce infective spores for up to 2 years in dead parts of infected plants. Prune in late summer when the weather is dry.
2. Plant resistant evergreens. Susceptibility to Phomopsis blight varies considerably among junipers. Ask for resistant stock at your garden or landscape center or consider planting another type of evergreen.
3. Fungicides. Bordeaux mixture, other copper-based fungicides, and mancozeb are labeled for use on Phomopsis. These fungicides can be applied 3–4 times in the spring, at 10–14 day intervals to protect the new growth. They can be used anytime a flush of new growth occurs. Once the new growth matures in midsummer, discontinue further applications.
Symptoms and Diagnosis
The first sign of infection is the browning of needle tips. New shoots, in the yellow-green stage, will brown and die in their first summer. Progressive dieback follows, eventually killing an entire branch by girdling the stem. The fungus will progress to the main stem and can infect and girdle stems less than 1/2 inch in diameter. Infected needles turn light green, then reddish-brown, and finally an ashen gray.
Life Cycle
Phomopsis overwinters on needles and stems of young trees that were infected the previous year. The fungus is most abundant on dead tissue that has become ashen gray in color. Infective spores are dispersed by rain splash. Only seven hours of 100% humidity are needed for infection to occur when temperatures are 75 degrees F.
Integrated Pest Management Strategies
1. Prune infected branches to prevent the spread of the disease. Remove dead tissue as well. The fungus can produce infective spores for up to 2 years in dead parts of infected plants. Prune in late summer when the weather is dry.
2. Plant resistant evergreens. Susceptibility to Phomopsis blight varies considerably among junipers. Ask for resistant stock at your garden or landscape center or consider planting another type of evergreen.
3. Fungicides. Bordeaux mixture, other copper-based fungicides, and mancozeb are labeled for use on Phomopsis. These fungicides can be applied 3–4 times in the spring, at 10–14 day intervals to protect the new growth. They can be used anytime a flush of new growth occurs. Once the new growth matures in midsummer, discontinue further applications.
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文章
Dummer. ゛☀
2017年09月18日
Pestalotiopsis is a type of needle blight fungal disease that is primarily found on arborvitae (Thuja). It is usually considered a secondary disease that attacks foliage that has been injured or weakened by unfavorable weather or growing conditions. The disease may kill the smaller twigs where the infected needles died.
Symptoms and Diagnosis
The blight usually starts at the tip of the foliage and progresses towards the leaf base. Affected foliage color progresses from green to yellowish, then to a dark brown that looks almost black. Twig tips can also turn brown and have black, pimple-like, pinhead size, fungal fruiting structures dotting the surface. Usually, killed foliage is near the base of the plant where foliage is relatively dense. The plants may appear scorched.
Life Cycle
Infections can occur at anytime of year. However, spring is the most likely time because favorable weather conditions exist and plants are showing stress from winter conditions.
Integrated Pest Management Strategies
1. Avoid over crowding plants to allow for sufficient sunlight and air circulation.
2. Keep plants healthy with good cultural practices. Follow proper watering, fertilization practices and minimize any mechanical and snow/ice damage, etc. that could cause an entry point for the fungus.
3. Prune out dead foliage and twigs as soon as possible.
4. Application of fungicides should not be necessary. If necessary in certain circumstances (e.g. a nursery), copper fungicides are registered for this use as a preventative. Always read and follow product label directions before application to plants.
Symptoms and Diagnosis
The blight usually starts at the tip of the foliage and progresses towards the leaf base. Affected foliage color progresses from green to yellowish, then to a dark brown that looks almost black. Twig tips can also turn brown and have black, pimple-like, pinhead size, fungal fruiting structures dotting the surface. Usually, killed foliage is near the base of the plant where foliage is relatively dense. The plants may appear scorched.
Life Cycle
Infections can occur at anytime of year. However, spring is the most likely time because favorable weather conditions exist and plants are showing stress from winter conditions.
Integrated Pest Management Strategies
1. Avoid over crowding plants to allow for sufficient sunlight and air circulation.
2. Keep plants healthy with good cultural practices. Follow proper watering, fertilization practices and minimize any mechanical and snow/ice damage, etc. that could cause an entry point for the fungus.
3. Prune out dead foliage and twigs as soon as possible.
4. Application of fungicides should not be necessary. If necessary in certain circumstances (e.g. a nursery), copper fungicides are registered for this use as a preventative. Always read and follow product label directions before application to plants.
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文章
Dummer. ゛☀
2017年09月18日
Dothistroma blight is a foliar disease of a number of pine species throughout the Midwest. Austrian pine is the primary host plant in Missouri. This blight is caused by the fungus Dothistroma pini, which infects and kills needles. The disease makes pines in landscapes unsightly and successive years of infection can result in decline and death of the tree.
Symptoms and Diagnosis
The earliest observable symptoms are dark-green bands and tan spots or bands on the mature needles. The spots and bands later turn reddish-brown. The needles will begin to die back from the tip, but needle bases usually remain green. From the time symptoms are first noticed to the time of needle browning may take 2–3 weeks. Infected needles will drop prematurely. Infection typically is most severe in the lower crown of the tree, closer to the inoculum that spreads from infected needles that have fallen from the tree.
Life Cycle
Dothistroma overwinters in infected needles. The infective spores are released during wet weather and dispersed by rain splash throughout the growing season. Because of the continual release of spores, infections can occur anytime from late April to late October. The fungus attacks the mature foliage; current season's needles are resistant until they are fully mature. Symptoms on newly infected tissue are especially obvious in early fall.
Integrated Pest Management Strategies
1. Live with the disease but monitor yearly. This disease is slow to spread. Annual spraying is not necessary in residential plantings. Wait and see how serious the problem becomes in one season. Serious infections can be prevented in the next growing season with the use of fungicides.
2. Plant resistant pines.Research on Austrian pine has determined that some populations are highly resistant to Dothistroma. Ask for these at your local garden center or nursery. Choose other nonsusceptible evergreens.
3. Apply fungicides. Adequate control of Dothistroma blight can be achieved with one or two sprays in late spring using a copper-based fungicides such as Bordeaux mixture. The first spray in early to mid-May protects mature foliage. A second spray in mid- June will protect the current season's needles which are resistant until they are fully grown. Other protectant fungicides include chlorothalonil (Daconil), Mancozeb and pentachloronitrobenzene.
Symptoms and Diagnosis
The earliest observable symptoms are dark-green bands and tan spots or bands on the mature needles. The spots and bands later turn reddish-brown. The needles will begin to die back from the tip, but needle bases usually remain green. From the time symptoms are first noticed to the time of needle browning may take 2–3 weeks. Infected needles will drop prematurely. Infection typically is most severe in the lower crown of the tree, closer to the inoculum that spreads from infected needles that have fallen from the tree.
Life Cycle
Dothistroma overwinters in infected needles. The infective spores are released during wet weather and dispersed by rain splash throughout the growing season. Because of the continual release of spores, infections can occur anytime from late April to late October. The fungus attacks the mature foliage; current season's needles are resistant until they are fully mature. Symptoms on newly infected tissue are especially obvious in early fall.
Integrated Pest Management Strategies
1. Live with the disease but monitor yearly. This disease is slow to spread. Annual spraying is not necessary in residential plantings. Wait and see how serious the problem becomes in one season. Serious infections can be prevented in the next growing season with the use of fungicides.
2. Plant resistant pines.Research on Austrian pine has determined that some populations are highly resistant to Dothistroma. Ask for these at your local garden center or nursery. Choose other nonsusceptible evergreens.
3. Apply fungicides. Adequate control of Dothistroma blight can be achieved with one or two sprays in late spring using a copper-based fungicides such as Bordeaux mixture. The first spray in early to mid-May protects mature foliage. A second spray in mid- June will protect the current season's needles which are resistant until they are fully grown. Other protectant fungicides include chlorothalonil (Daconil), Mancozeb and pentachloronitrobenzene.
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文章
Dummer. ゛☀
2017年09月18日
Cytospora canker is caused by a fungus, Leucostoma kunzei (formerly known as Cytospora kunzei). In its perfect stage, it is known as Valsa kunzei. It is a destructive disease of many of the spruces, especially Colorado blue and Norway spruces, from the Midwest to New England. The disease is more common on trees over 15 years old and trees under stress and of low vigor. Trees with shallow roots, weakened by mechanical injury, insect, or weather stresses, and trees growing on unfavorable sites are most susceptible. The disease destroys the symmetry of spruce trees and in time may kill them. Infections on Colorado blue spruces are usually confined to branches. Branches and trunks are damaged on black, Engelmann, Norway, red, and white spruces. Cytospora cankers have also been found on Douglas fir, hemlock, larch, and balsam fir.
Symptoms and Diagnosis
Dying of lower branches is usually the first symptom. The needles turn brown and after a few months drop off, and white or light blue patches of resin become obvious on the dead bark of larger branches. As the disease progresses over several years, higher branches also die. Dead areas called cankers are formed. The infected inner bark tissue and cambium are brown in contrast to the normal light color of healthy tissue, but the wood beneath the infected bark is not discolored. As cankers enlarge and girdle the stem, parts above the diseased area lose color, make little growth, wilt or wither, and die back from the tips. Infected branches often start growth later in the spring. The resin exuded from cankered branches is visible on dead bark after infected needles are cast. This is the most obvious symptom on infected branches.
Life Cycle
The fungus overwinters in cankered bark. Spores from fruiting bodies formed in cankers are spread by rain, wind, insects, birds, and man. Infection occurs through wounds. The fungus grows and kills the bark, then expands until the entire branch is killed from the branch being girdled.
Integrated Pest Management Strategies
1. Prune out diseased branches. Prune out all infected branches and burn or remove them from the site. Prune in late winter when it is sunny and the trees are dry. Dip pruning tools into a solution of 1–part bleach and 9–parts water between cuts to reduce spreading the disease. After pruning, oil blades to prevent rust.
2. Avoid injuries to bark and stems. Wounds can provide entry points for the pathogen, especially during wet periods.
3.Improve plant health. Water during dry periods and aerate the soil around the tree to relieve soil compaction and facilitate water and nutrient penetration. Fertilize to maintain vigor.
4. Maintain good air circulation. Chances of infection are greater on plants that are crowded together. Space plants out when planting to accommodate mature growth.
5. Fungicidal sprays are seldom effective and are not recommended. Once the tree is infected, the disease is difficult to control. Bordeaux mixture or other copper-containing fungicides may help slow the spread of the disease. The best time to apply fungicides has not been established. Consider using fungicidal sprays only if the tree is very valuable and you are willing to pay for regular sprayings.
6. Remove the infected tree and plant a different species or variety. Blue and Norway spruce are most susceptible to Cytospora canker.
Symptoms and Diagnosis
Dying of lower branches is usually the first symptom. The needles turn brown and after a few months drop off, and white or light blue patches of resin become obvious on the dead bark of larger branches. As the disease progresses over several years, higher branches also die. Dead areas called cankers are formed. The infected inner bark tissue and cambium are brown in contrast to the normal light color of healthy tissue, but the wood beneath the infected bark is not discolored. As cankers enlarge and girdle the stem, parts above the diseased area lose color, make little growth, wilt or wither, and die back from the tips. Infected branches often start growth later in the spring. The resin exuded from cankered branches is visible on dead bark after infected needles are cast. This is the most obvious symptom on infected branches.
Life Cycle
The fungus overwinters in cankered bark. Spores from fruiting bodies formed in cankers are spread by rain, wind, insects, birds, and man. Infection occurs through wounds. The fungus grows and kills the bark, then expands until the entire branch is killed from the branch being girdled.
Integrated Pest Management Strategies
1. Prune out diseased branches. Prune out all infected branches and burn or remove them from the site. Prune in late winter when it is sunny and the trees are dry. Dip pruning tools into a solution of 1–part bleach and 9–parts water between cuts to reduce spreading the disease. After pruning, oil blades to prevent rust.
2. Avoid injuries to bark and stems. Wounds can provide entry points for the pathogen, especially during wet periods.
3.Improve plant health. Water during dry periods and aerate the soil around the tree to relieve soil compaction and facilitate water and nutrient penetration. Fertilize to maintain vigor.
4. Maintain good air circulation. Chances of infection are greater on plants that are crowded together. Space plants out when planting to accommodate mature growth.
5. Fungicidal sprays are seldom effective and are not recommended. Once the tree is infected, the disease is difficult to control. Bordeaux mixture or other copper-containing fungicides may help slow the spread of the disease. The best time to apply fungicides has not been established. Consider using fungicidal sprays only if the tree is very valuable and you are willing to pay for regular sprayings.
6. Remove the infected tree and plant a different species or variety. Blue and Norway spruce are most susceptible to Cytospora canker.
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文章
Dummer. ゛☀
2017年09月18日
Brown spot needle blight is a fungal disease of pines caused by Mycosphaerella dearnessii. It affects much pine in the Midwest including mugo, Japanese black, Virginia, eastern white pine, and most noticeably Scots pine. It is similar in appearance and can be confused with Dothistroma needle blight which is more commonly found on Austrian and ponderosa pine in the St. Louis area.
It generally starts on the lower branches and moves up the tree. It also favors the north side of the plant which is more humid. The blight is most damaging on small trees but over time can retard growth and weaken mature trees.
Symptoms and Diagnosis
Dead needles, which turn brown or a burnt red-orange and then drop is characteristic of the disease. The loss of 2nd and 3rd needles is accelerated and branches may look bare except for small tufts of needles at the tips. Damage usually begins on lower branches first. Yellow to tan spots first appear in May to September on current year needles. Brown spots appear mid to late summer and coalescing into bands encircling the needles and causing death of parts beyond the band. The bands may occur at any location along the length of the needle. Resin may appear on the spots. By fall the spots may appear resin-soaked. By late summer/autumn yellow halos may surround brown bands and spots. Straw-colored lesions becoming light tan with a dark border may appear raised as surrounding, uninfected tissue dies. Dead needles drop in fall.
Life Cycle
In late spring to early summer spores on dead needles initiate new infections through stomata on the needles. June-July is the most active infection period. In late summer, fruiting bodies called pycnidia form on infected needles in the tree and on the ground. The spores spread by splashing rain to new infection sites. Infection is favored by warm, humid conditions.
Integrated Pest Management Strategies
1. Live with the disease. If damage is slight you may decide just to live with a few browning needles. The plant can easily survive light infections.
2. Sanitation. Remove and dispose of diseased needle on the tree if practical and most certainly those on the ground as these are the source of on-going infection.
3. Refrain from overhead watering. Since splashing water spreads the spores, limit overhead watering or do so only early in the day so the needles dry quickly.
4. Improve air circulation. High humidity and slow drying needles fosters infection so prune out dense foliage and evaluate nearby plants to see if pruning them might promote faster drying of the pine's needles. Provide ample spacing between plants.
5. Use fungicides. copper-based fungicides such as Bordeaux mixture are effective as a protectant. Other protectant fungicides include chlorothalonil (Daconil) and Mancozeb. Follow label directions for application.
6. Plant resistant pines or other plants. Consider replacing the pines with a species that is more resistant to the disease or an evergreen other than a pine, such as spruce, arborvitae, or juniper.
It generally starts on the lower branches and moves up the tree. It also favors the north side of the plant which is more humid. The blight is most damaging on small trees but over time can retard growth and weaken mature trees.
Symptoms and Diagnosis
Dead needles, which turn brown or a burnt red-orange and then drop is characteristic of the disease. The loss of 2nd and 3rd needles is accelerated and branches may look bare except for small tufts of needles at the tips. Damage usually begins on lower branches first. Yellow to tan spots first appear in May to September on current year needles. Brown spots appear mid to late summer and coalescing into bands encircling the needles and causing death of parts beyond the band. The bands may occur at any location along the length of the needle. Resin may appear on the spots. By fall the spots may appear resin-soaked. By late summer/autumn yellow halos may surround brown bands and spots. Straw-colored lesions becoming light tan with a dark border may appear raised as surrounding, uninfected tissue dies. Dead needles drop in fall.
Life Cycle
In late spring to early summer spores on dead needles initiate new infections through stomata on the needles. June-July is the most active infection period. In late summer, fruiting bodies called pycnidia form on infected needles in the tree and on the ground. The spores spread by splashing rain to new infection sites. Infection is favored by warm, humid conditions.
Integrated Pest Management Strategies
1. Live with the disease. If damage is slight you may decide just to live with a few browning needles. The plant can easily survive light infections.
2. Sanitation. Remove and dispose of diseased needle on the tree if practical and most certainly those on the ground as these are the source of on-going infection.
3. Refrain from overhead watering. Since splashing water spreads the spores, limit overhead watering or do so only early in the day so the needles dry quickly.
4. Improve air circulation. High humidity and slow drying needles fosters infection so prune out dense foliage and evaluate nearby plants to see if pruning them might promote faster drying of the pine's needles. Provide ample spacing between plants.
5. Use fungicides. copper-based fungicides such as Bordeaux mixture are effective as a protectant. Other protectant fungicides include chlorothalonil (Daconil) and Mancozeb. Follow label directions for application.
6. Plant resistant pines or other plants. Consider replacing the pines with a species that is more resistant to the disease or an evergreen other than a pine, such as spruce, arborvitae, or juniper.
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文章
Dummer. ゛☀
2017年09月17日
Pythium blight, also called cottony blight or grease spot, is a fungal disease of turfgrasses. All turfgrasses, warm and cool season, are susceptible to attack. This disease is most common during hot, very humid weather especially in golf courses, less so in home lawns. The disease can spread rapidly, killing large areas of seedling or established turf in as little as a day during conditions of high temperature (80 degrees to 90 degrees F), high soil moisture, and little air movement. The disease can also occur at lower temperatures during cool (55 degrees to 65 degrees F) wet weather. When root and crown tissue is attacked, Pythium root and crown rot results. This disease occurs mostly during warm to hot weather. Wet, humid conditions favor the disease.
Symptoms and Diagnosis
Pythium blight is most readily recognized as small spots or patches of blighted grass that suddenly appear during warm, wet periods. In the early stages, the grass leaves may appear water-soaked, slimy (greasy), and dark. As the disease progresses, the leaves shrivel and the patches fade from green to light brown. When observing these patches in early morning, cottony fungal growth can usually be seen on the foliage, although not always.
In many cases, these patches develop into diffused streaks that follow water drainage patterns or mowing patterns. These streaks are caused by the water or equipment picking up the fungus and spreading it along its path. Under favorable conditions for the disease development, these streaks may coalesce to form large areas of dead grass. If a sudden drop in temperature or humidity or the application of a fungicide halts the development of Pythium blight, distinct strawcolored spots develop. Grass blades may twist and collapse at the lesion.
Life Cycle
The pathogen survives over winter and periods adverse to disease development as spores associated with debris in the soil. It can be moved from one area to another by soil movement, by transporting diseased plants or plant parts, and by equipment, shoes, or surface water.
Damping-off, seed decay, or a seedling blight of turf grasses can also be caused by Pythium fungi. These fungi may also attack the plant roots and crowns, causing reduced growth, off-color, and thinning (Pythium root and crown rot).
Diseased plants serve as infection centers from which the pathogen spreads. Movement from these areas can be rapid in wet or humid, hot weather. High nitrogen fertility favors the disease on many grass varieties. Alkaline- or calcium-deficient soils also tend to favor the disease.
Integrated Pest Management Strategies
1. Fertilizer. Maintain grass growth by low to moderate rates of balanced fertilizers. Maintain soil pH in the neutral to slightly acid range. Test the soil every 3–5 years to understand and correct nutrient deficiencies.
2. Watering. If your lawn has the disease, do not water in the late afternoon or early evening. Generally speaking, water in the early morning.
3. Thatch. Remove thatch when greater than 1/2 inch.
4. Pruning. Selectively prune trees and shrubs growing near the area to improve air circulation.
5. Mowing. Increasing the mowing height and following other practices that promote good root growth will lessen damage from Pythium root rot.
6.Fungicides. A preventive fungicide program may be needed to stop the development of Pythium during extended periods of warm, humid weather. Applications of fungicides recommended for control of Pythium blights should be made to areas with a history of Pythium activity when conditions are favorable for development or when symptoms first appear. Repeat applications as necessary. Fungicide applications may be needed 7 to 21 days after planting to protect young seedlings and more often during high rainfall periods. Pesticides registered for use include chlorothalonil (Daconil), fosetyl-Al, mancozeb, and maneb.
Organic Strategies
Strategies 2, 3, 4 and 5 are strictly organic approaches. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 1.
Symptoms and Diagnosis
Pythium blight is most readily recognized as small spots or patches of blighted grass that suddenly appear during warm, wet periods. In the early stages, the grass leaves may appear water-soaked, slimy (greasy), and dark. As the disease progresses, the leaves shrivel and the patches fade from green to light brown. When observing these patches in early morning, cottony fungal growth can usually be seen on the foliage, although not always.
In many cases, these patches develop into diffused streaks that follow water drainage patterns or mowing patterns. These streaks are caused by the water or equipment picking up the fungus and spreading it along its path. Under favorable conditions for the disease development, these streaks may coalesce to form large areas of dead grass. If a sudden drop in temperature or humidity or the application of a fungicide halts the development of Pythium blight, distinct strawcolored spots develop. Grass blades may twist and collapse at the lesion.
Life Cycle
The pathogen survives over winter and periods adverse to disease development as spores associated with debris in the soil. It can be moved from one area to another by soil movement, by transporting diseased plants or plant parts, and by equipment, shoes, or surface water.
Damping-off, seed decay, or a seedling blight of turf grasses can also be caused by Pythium fungi. These fungi may also attack the plant roots and crowns, causing reduced growth, off-color, and thinning (Pythium root and crown rot).
Diseased plants serve as infection centers from which the pathogen spreads. Movement from these areas can be rapid in wet or humid, hot weather. High nitrogen fertility favors the disease on many grass varieties. Alkaline- or calcium-deficient soils also tend to favor the disease.
Integrated Pest Management Strategies
1. Fertilizer. Maintain grass growth by low to moderate rates of balanced fertilizers. Maintain soil pH in the neutral to slightly acid range. Test the soil every 3–5 years to understand and correct nutrient deficiencies.
2. Watering. If your lawn has the disease, do not water in the late afternoon or early evening. Generally speaking, water in the early morning.
3. Thatch. Remove thatch when greater than 1/2 inch.
4. Pruning. Selectively prune trees and shrubs growing near the area to improve air circulation.
5. Mowing. Increasing the mowing height and following other practices that promote good root growth will lessen damage from Pythium root rot.
6.Fungicides. A preventive fungicide program may be needed to stop the development of Pythium during extended periods of warm, humid weather. Applications of fungicides recommended for control of Pythium blights should be made to areas with a history of Pythium activity when conditions are favorable for development or when symptoms first appear. Repeat applications as necessary. Fungicide applications may be needed 7 to 21 days after planting to protect young seedlings and more often during high rainfall periods. Pesticides registered for use include chlorothalonil (Daconil), fosetyl-Al, mancozeb, and maneb.
Organic Strategies
Strategies 2, 3, 4 and 5 are strictly organic approaches. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 1.
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文章
Dummer. ゛☀
2017年09月17日
Powdery mildew is a common fungal disease of indoor plants. African violets, begonias, ivy, jade, kalanchoe, poinsettia and rosemary are susceptible to powdery mildew. It thrives best in cool, damp conditions.
Symptoms and Diagnosis
Powdery mildew starts as a dusty, white to gray, thread-like coating over leaf surfaces, stems, buds or flowers. It can be partially removed by rubbing the leaves but this will not eliminate the fungus.
Life Cycle
Powdery mildew is caused by many species of fungi each responsible for causing the disease on a limited number of plant species. That is, the species of fungi that causes powdery mildew on African violets is not the same species that causes powder mildew on rosemary. Therefore, powdery mildew on one plant may not spread to a dissimilar plant. Even given this, both plants may develop powdery mildew from different species of fungi if favorable conditions exist for disease development. Several species of powdery mildew can be common both indoors and out.
Powdery mildew starts as discrete, circular powdery white spots on leaves. It may also be on other above ground plant parts. The fungal mycelium grows and in time can cover large parts of the plant giving them a dusty, powdery, or silvery appearance. Powdery spores are produced that spread to other parts of the plant or related plants. The disease can develop and spread anytime the conditions for growth are favorable. Photosynthesis is impaired and growth may be stunted. Buds fail to mature. The plant declines in growth and vigor and eventually becomes unsightly.
Integrated Pest Management
1. Don’t ask for a problem. Choose healthy plants and purchase mildew resistant cultivars if possible.
2. Sanitation. At the first sign of infection, isolate the plant. Remove and dispose of all infected plant parts. Discard severely infected plants.
3. Evaluate and modify the growth environment. Keep plants in a well-ventilated area and do not overcrowd. Improve air circulation around plants. Avoid wetting leaves when watering, do not water from above.
4. Don’t over fertilize. Avoid high nitrogen fertilizers since powdery mildew attacks new succulent growth.
5. Treat with baking soda. Some gardeners recommend applying a baking soda solution to prevent the fungi from establishing. This changes the pH of the leaf surface. Test on a few leaves first as this may damage some plants. Some may feel this treatment may look as unsightly as the mildew disease itself.
6. Use a commercial fungicide. Valuable plants or crops may require the application of an appropriate fungicide labeled for indoor use, preferably one that is systemic. Be sure to read the label and follow directions.
Symptoms and Diagnosis
Powdery mildew starts as a dusty, white to gray, thread-like coating over leaf surfaces, stems, buds or flowers. It can be partially removed by rubbing the leaves but this will not eliminate the fungus.
Life Cycle
Powdery mildew is caused by many species of fungi each responsible for causing the disease on a limited number of plant species. That is, the species of fungi that causes powdery mildew on African violets is not the same species that causes powder mildew on rosemary. Therefore, powdery mildew on one plant may not spread to a dissimilar plant. Even given this, both plants may develop powdery mildew from different species of fungi if favorable conditions exist for disease development. Several species of powdery mildew can be common both indoors and out.
Powdery mildew starts as discrete, circular powdery white spots on leaves. It may also be on other above ground plant parts. The fungal mycelium grows and in time can cover large parts of the plant giving them a dusty, powdery, or silvery appearance. Powdery spores are produced that spread to other parts of the plant or related plants. The disease can develop and spread anytime the conditions for growth are favorable. Photosynthesis is impaired and growth may be stunted. Buds fail to mature. The plant declines in growth and vigor and eventually becomes unsightly.
Integrated Pest Management
1. Don’t ask for a problem. Choose healthy plants and purchase mildew resistant cultivars if possible.
2. Sanitation. At the first sign of infection, isolate the plant. Remove and dispose of all infected plant parts. Discard severely infected plants.
3. Evaluate and modify the growth environment. Keep plants in a well-ventilated area and do not overcrowd. Improve air circulation around plants. Avoid wetting leaves when watering, do not water from above.
4. Don’t over fertilize. Avoid high nitrogen fertilizers since powdery mildew attacks new succulent growth.
5. Treat with baking soda. Some gardeners recommend applying a baking soda solution to prevent the fungi from establishing. This changes the pH of the leaf surface. Test on a few leaves first as this may damage some plants. Some may feel this treatment may look as unsightly as the mildew disease itself.
6. Use a commercial fungicide. Valuable plants or crops may require the application of an appropriate fungicide labeled for indoor use, preferably one that is systemic. Be sure to read the label and follow directions.
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文章
Dummer. ゛☀
2017年09月17日
Many ornamental trees and shrubs are susceptible to Phytophthora root rot and can develop root and crown rot, particularly if the soil around the base of the plant remains wet for long periods of time. Typical symptoms of a root disease are apparent on infected plants. The leaves will appear droughtstressed and may die quickly as the weather warms in late spring or early summer. Trees that are especially susceptible include oak and dogwood.
Symptoms and Diagnosis
Leaves will appear drought stressed, sometimes turning dull green, yellow, red, or purple as they wilt. Infected trees may survive a few years before the disease kills the whole plant. The bark around the soil-line may appear darkened. Cutting away some bark should reveal red-brown discoloration in the wood underneath it. Disease symptoms are distinguishable from Armillaria root rot because mycelial mats do not develop in tissues infected with Phytophthora root rot.
Life Cycle
Root rot-causing Phytophthora species can survive in the soil for years, as long as moist conditions persist. It can spread through splashing rain, irrigation water, and runoff water. Disease fungi can spread through contaminated soil and garden equipment as well. Rot is more likely to spread in early spring and late fall during cool, rainy weather. But symptoms are more likely during stress periods of low rainfall. Flooded and saturated soil conditions for 6–8 hours are especially conducive to the spread of root rots. Wounds are not required for infection.
Integrated Pest Management Strategies
1. Improve water drainage. Prior to planting, make amendments to the soil composition to help manage drainage away from tree roots. Don’t allow water to pool around the collar or root system. Core aerate to improve drainage and lessen compaction.
2. Raise the planting site to avoid poor drainage and prevent pools of standing water from forming around valuable ornamentals. Plant on mounds of soil. Never plant trees deeper than they were planted at the nursery.
3. Separate plants, shrubs, and trees according to their irrigation needs, and avoid overwatering.
4. Remove soil. If soil has been piled up over the crown, remove it carefully to expose root flare. This is where fungal infection is likely to occur.
5. Plant resistant or less susceptible varieties. Consider replanting with tolerant plants after Phytophthora root rot has been diagnosed. Trees that are tolerant to Phytophthora root rot include white cedar and American arborvitae.
Symptoms and Diagnosis
Leaves will appear drought stressed, sometimes turning dull green, yellow, red, or purple as they wilt. Infected trees may survive a few years before the disease kills the whole plant. The bark around the soil-line may appear darkened. Cutting away some bark should reveal red-brown discoloration in the wood underneath it. Disease symptoms are distinguishable from Armillaria root rot because mycelial mats do not develop in tissues infected with Phytophthora root rot.
Life Cycle
Root rot-causing Phytophthora species can survive in the soil for years, as long as moist conditions persist. It can spread through splashing rain, irrigation water, and runoff water. Disease fungi can spread through contaminated soil and garden equipment as well. Rot is more likely to spread in early spring and late fall during cool, rainy weather. But symptoms are more likely during stress periods of low rainfall. Flooded and saturated soil conditions for 6–8 hours are especially conducive to the spread of root rots. Wounds are not required for infection.
Integrated Pest Management Strategies
1. Improve water drainage. Prior to planting, make amendments to the soil composition to help manage drainage away from tree roots. Don’t allow water to pool around the collar or root system. Core aerate to improve drainage and lessen compaction.
2. Raise the planting site to avoid poor drainage and prevent pools of standing water from forming around valuable ornamentals. Plant on mounds of soil. Never plant trees deeper than they were planted at the nursery.
3. Separate plants, shrubs, and trees according to their irrigation needs, and avoid overwatering.
4. Remove soil. If soil has been piled up over the crown, remove it carefully to expose root flare. This is where fungal infection is likely to occur.
5. Plant resistant or less susceptible varieties. Consider replanting with tolerant plants after Phytophthora root rot has been diagnosed. Trees that are tolerant to Phytophthora root rot include white cedar and American arborvitae.
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文章
Dummer. ゛☀
2017年09月17日
Peach leaf curl is a springtime disease caused by the fungus, Taphrina deformans. It infects the leaves and shoots of peaches and nectarines. Apricots are immune. It is one of the most common diseases of these fruits. It causes the leaves to curl and turn reddish in color. A severe infection can cause reduced yields. 
Symptoms and Diagnosis
Symptoms first appear in spring. New leaves become curled and develop reddish areas. The reddish areas become thickened and puckered resulting in severely distorted leaves. As the disease progresses, the thickened areas turn yellowish gray and become covered with velvety spores. Affected leaves turn yellow or brown and fall prematurely. Affected shoots usually send out new leaves which often are unaffected by the disease unless rainy weather ensues. In more severe infections, shoots may become thickened and die.
Aphids can also cause leaves to curl. If present, the insects or cast skins will be evident to the naked eye.
Life Cycle
The fungus overwinters on bud scales, on twigs, and on fallen infected leaves. In spring the fungal spores are splashed onto newly developing leaves. During cool, wet weather the spores germinate on the young leaves and initiate infection. Development of the disease slows as temperatures increase. Older leaves are resistant to infection. Consequently, the disease is most prevalent in the spring.
Integrated Pest Management Strategies
1. Keep plant healthy — avoid excess fertilization. A healthy plant can better withstand the loss of leaves, but excess fertilization can cause succulent tissue that is very susceptible to infection.
2. Clean up diseased leaves. Raking up and disposing of diseased leaves can't hurt, but its value in controlling the disease is slight.
3. Don't panic.Once infection has occurred fungicidal sprays are not effective. A healthy plant should refoliate. Because refoliation normally occurs during warmer, dryer weather, re-infection is usually not a problem. Thinning the fruit crop in years of severe infection can also help maintain plant vigor. To limit damage the year after a moderate to severe infection, follow the protective spray program below.
4. Use properly timed protective fungicidal sprays. If leaf curl was a problem in the spring, apply a protective fungicidal spray after leaf fall in October or November or before bud break in late winter, January through February. After buds have begun to swell fungicidal sprays are not satisfactory. Do not apply to foliage. Chemicals effective in controlling leaf curl include copper-based fungicides like Bordeaux mixture, Bravo, lime-sulfur spray, or other brands that list the control of peach leaf curl on their label.
5. Replace the tree with a more disease tolerant variety. If you want to avoid using fungicidal sprays, consider replacing the tree with a more tolerant variety. ‘Redhaven’ and cultivars derived from ‘Redhaven’ have greater tolerance to peach leaf curl disease.
Symptoms and Diagnosis
Symptoms first appear in spring. New leaves become curled and develop reddish areas. The reddish areas become thickened and puckered resulting in severely distorted leaves. As the disease progresses, the thickened areas turn yellowish gray and become covered with velvety spores. Affected leaves turn yellow or brown and fall prematurely. Affected shoots usually send out new leaves which often are unaffected by the disease unless rainy weather ensues. In more severe infections, shoots may become thickened and die.
Aphids can also cause leaves to curl. If present, the insects or cast skins will be evident to the naked eye.
Life Cycle
The fungus overwinters on bud scales, on twigs, and on fallen infected leaves. In spring the fungal spores are splashed onto newly developing leaves. During cool, wet weather the spores germinate on the young leaves and initiate infection. Development of the disease slows as temperatures increase. Older leaves are resistant to infection. Consequently, the disease is most prevalent in the spring.
Integrated Pest Management Strategies
1. Keep plant healthy — avoid excess fertilization. A healthy plant can better withstand the loss of leaves, but excess fertilization can cause succulent tissue that is very susceptible to infection.
2. Clean up diseased leaves. Raking up and disposing of diseased leaves can't hurt, but its value in controlling the disease is slight.
3. Don't panic.Once infection has occurred fungicidal sprays are not effective. A healthy plant should refoliate. Because refoliation normally occurs during warmer, dryer weather, re-infection is usually not a problem. Thinning the fruit crop in years of severe infection can also help maintain plant vigor. To limit damage the year after a moderate to severe infection, follow the protective spray program below.
4. Use properly timed protective fungicidal sprays. If leaf curl was a problem in the spring, apply a protective fungicidal spray after leaf fall in October or November or before bud break in late winter, January through February. After buds have begun to swell fungicidal sprays are not satisfactory. Do not apply to foliage. Chemicals effective in controlling leaf curl include copper-based fungicides like Bordeaux mixture, Bravo, lime-sulfur spray, or other brands that list the control of peach leaf curl on their label.
5. Replace the tree with a more disease tolerant variety. If you want to avoid using fungicidal sprays, consider replacing the tree with a more tolerant variety. ‘Redhaven’ and cultivars derived from ‘Redhaven’ have greater tolerance to peach leaf curl disease.
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文章
Dummer. ゛☀
2017年09月17日
Gummosis is the oozing of sap from wounds or cankers on fruit trees. Gummosis can result from environmental stress, mechanical injury, or disease and insect infestation. Cytospora canker or Valsa canker, the fungal cause of gummosis, affects stone fruit trees like apricot, cherry, peach, and plum. Cytospora infection is distinguishable from insect damage and mechanical injuries because sawdust or pieces of bark are not mixed in the sap, as it would be with insect or mechanical damage. Cytospora canker is also known as perennial canker.
Symptoms and Diagnosis
On trees infected with Cytospora canker, new shoots or leaves may turn yellow or wilt. Sunken lesions develop on the bark. These lesions enlarge, and gummy, amber-colored sap oozes from the bark. Curly orange threads (fungal chains) may grow out of the bark as the disease progresses. Leaves may brown and drop. The disease kills the wood underneath the cankers, often causing whole branches to die. Infected wood and the defoliation that may occur weakens the tree, but if the disease infects the trunk, the whole tree may die.
Life Cycle
Cytospora canker is caused by one of two different fungi. The fungus overwinters on dead wood or in sunken lesions. Curly orange fungal chains will release spores in the spring which are distributed by winds and rain splash. Once the spores land on a host tree, they enter through wounds made from insect boring, mechanical injuries, or winter injury. Symptoms are more prevalent during warm (70–85 degrees F), wet spring weather as the moisture facilitates entry into wounds. Trees just coming out of dormancy are most susceptible to the pathogen.
Integrated Pest Management Strategies
1. Be careful not to damage trunks with lawn mowers or other yard and garden equipment. Fungal spores enter the tree through injured tissue where they germinate and penetrate the tissue. This is the primary mode of infection.
2. Take steps to prevent winter injuries. Plant in well-drained soils or amend soils to improve drainage as needed. Avoid planting in open or windy areas to reduce desiccation. Select winterhardy cultivars matched to your hardiness zone. Paint the lower branches and trunks of 1–3 year old trees with white latex paint to reduce cold damage.
3. Proper care and maintenance. Prevent insect boring damage by maintaining the health of the tree. Prune and dispose of diseased branches in late winter. Burn infected wood, if possible.
4. Plant more resistant varieties. None of these are immune, but fungal development is slower if the disease becomes established.
Symptoms and Diagnosis
On trees infected with Cytospora canker, new shoots or leaves may turn yellow or wilt. Sunken lesions develop on the bark. These lesions enlarge, and gummy, amber-colored sap oozes from the bark. Curly orange threads (fungal chains) may grow out of the bark as the disease progresses. Leaves may brown and drop. The disease kills the wood underneath the cankers, often causing whole branches to die. Infected wood and the defoliation that may occur weakens the tree, but if the disease infects the trunk, the whole tree may die.
Life Cycle
Cytospora canker is caused by one of two different fungi. The fungus overwinters on dead wood or in sunken lesions. Curly orange fungal chains will release spores in the spring which are distributed by winds and rain splash. Once the spores land on a host tree, they enter through wounds made from insect boring, mechanical injuries, or winter injury. Symptoms are more prevalent during warm (70–85 degrees F), wet spring weather as the moisture facilitates entry into wounds. Trees just coming out of dormancy are most susceptible to the pathogen.
Integrated Pest Management Strategies
1. Be careful not to damage trunks with lawn mowers or other yard and garden equipment. Fungal spores enter the tree through injured tissue where they germinate and penetrate the tissue. This is the primary mode of infection.
2. Take steps to prevent winter injuries. Plant in well-drained soils or amend soils to improve drainage as needed. Avoid planting in open or windy areas to reduce desiccation. Select winterhardy cultivars matched to your hardiness zone. Paint the lower branches and trunks of 1–3 year old trees with white latex paint to reduce cold damage.
3. Proper care and maintenance. Prevent insect boring damage by maintaining the health of the tree. Prune and dispose of diseased branches in late winter. Burn infected wood, if possible.
4. Plant more resistant varieties. None of these are immune, but fungal development is slower if the disease becomes established.
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文章
Dummer. ゛☀
2017年09月17日
Downy mildew is an extremely serious fungal disease of grapes that can result in severe crop loss. It is caused by the fungus Plasmopara viticola.
Symptoms and Diagnosis
The pathogen attacks all green parts of the vine, especially the leaves. Lesions on leaves are angular, yellowish, sometimes oily, and located between the veins. As the disease progresses, a white cottony growth can be observed on the lower leaf surface.
Severely infected leaves will drop. If enough defoliation occurs, the overwintering buds will be more susceptible to winter injury. Infected shoot tips become thick, curl, and eventually turn brown and die. Young berries are highly susceptible, appearing grayish when infected. Berries become less susceptible when mature. Eventually, infected berries will drop.
Life Cycle
The fungus overwinters in diseased leaves on the ground. Spores are released in the spring and spread to the leaves and berries by splashing rain and wind. The fungus has two types of spores, both germinating into swimming spores. These spores swim to the stomates (breathing pores) of plants and initiate infection. Water is necessary for the spores to swim and infect, so outbreaks of the disease coincide with periods of wet weather. Downy mildew is favored by all factors that increase the moisture content of soil, air, and the plant, with rainfall being the principal factor for infection during the growing season. Downy mildew infection can become a severe problem when a wet winter is followed by a wet spring and a warm summer with frequent rainfall.
Integrated Pest Management Strategies
1. Maintain plant vigor. Make sure soils are welldrained. Fertilize according to soil test information obtained at least every other year.
2. Sanitation. Remove fallen leaves which are the source of overwintering inoculum.
3. Pruning. Prune out the ends of infected shoots.
4. Fungicides. Fungicides are an important control measure, especially on susceptible cultivars. They should be applied just before bloom, 7 to 10 days later (usually at the end of bloom), 10 to 14 days after that, and finally, 3 weeks after the third application. For cultivars very susceptible to downy mildew or where the disease was severe the previous season, an additional application is suggested about 2 weeks before the first blossom opens. Pesticides registered for use include captan, copper, fosetyl-Al, mancozeb, maneb, and ziram.
5. Cultivars. Select and plant resistant cultivars.
Symptoms and Diagnosis
The pathogen attacks all green parts of the vine, especially the leaves. Lesions on leaves are angular, yellowish, sometimes oily, and located between the veins. As the disease progresses, a white cottony growth can be observed on the lower leaf surface.
Severely infected leaves will drop. If enough defoliation occurs, the overwintering buds will be more susceptible to winter injury. Infected shoot tips become thick, curl, and eventually turn brown and die. Young berries are highly susceptible, appearing grayish when infected. Berries become less susceptible when mature. Eventually, infected berries will drop.
Life Cycle
The fungus overwinters in diseased leaves on the ground. Spores are released in the spring and spread to the leaves and berries by splashing rain and wind. The fungus has two types of spores, both germinating into swimming spores. These spores swim to the stomates (breathing pores) of plants and initiate infection. Water is necessary for the spores to swim and infect, so outbreaks of the disease coincide with periods of wet weather. Downy mildew is favored by all factors that increase the moisture content of soil, air, and the plant, with rainfall being the principal factor for infection during the growing season. Downy mildew infection can become a severe problem when a wet winter is followed by a wet spring and a warm summer with frequent rainfall.
Integrated Pest Management Strategies
1. Maintain plant vigor. Make sure soils are welldrained. Fertilize according to soil test information obtained at least every other year.
2. Sanitation. Remove fallen leaves which are the source of overwintering inoculum.
3. Pruning. Prune out the ends of infected shoots.
4. Fungicides. Fungicides are an important control measure, especially on susceptible cultivars. They should be applied just before bloom, 7 to 10 days later (usually at the end of bloom), 10 to 14 days after that, and finally, 3 weeks after the third application. For cultivars very susceptible to downy mildew or where the disease was severe the previous season, an additional application is suggested about 2 weeks before the first blossom opens. Pesticides registered for use include captan, copper, fosetyl-Al, mancozeb, maneb, and ziram.
5. Cultivars. Select and plant resistant cultivars.
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